Nico Williams on Barcelona can inflate his numbers by a lot with ease, i dont have any doubt about that.
Barcelona scores much more than Bilbao and he can provide a lot more of assits and plus he is gonna have much more clear chances to score also, the only perhaps i see is, maybe he doesnt have so much minutes, in Bilbao he plays all the minutes as an starter but here.... i dont know.
With the support of a better squad and manager tactics, Nico William productivity will definitely increase. I think Hansi Flick will make Nico William a key player in the main squad, Barcelona will not recruit him to be a second string player. Barcelona front line combination next season will look very sharp if Nico William is added, I think Barcelona has a striker who is no less great than Real Madrid.